1. Field of the Invention
The present invention relates to biological test packs for monitoring ethylene oxide sterilization cycles used in hospital sterilization procedures.
2. Description of the Prior Art
This invention relates to a disposable biological test pack used to monitor ethylene oxide gas sterilizers used in hospitals, clinics, and surgery centers. Sterilizers are used in these environments to sterilize reusable medical devices such as surgical instruments. To be maintained properly, the sterilization equipment must be tested periodically to validate performance. A common method to test the efficacy of the sterilizer is to place a biological indicator in the load to be sterilized. The theory is, if the sterilization cycle can kill a high concentration of highly resistant biological spores it is performing correctly. However, it is not sufficent to merely place a spore strip in the sterilizer. Instead hospital personnel have been trained to place a biological strip in a package as resistant to sterilization as the largest, most resistant package which the hospital is apt to sterilize.
The biological indicator used in medical institutions is generally comprised of a self-contained unit which includes a large number of bacterial spores dried onto a paper strip along with a specially prepared media broth which acts as the nutrient. The spores used are those which have previously been identified to be very resistant to ETO gas sterilization (bacillus subtillis). Typically, the self-contained unit of spores and media is placed in a loaded sterilizer for the full duration of a sterilization cycle. To authenticate the cycle, the self-contained unit is placed in a package similar to other wrapped items to be sterilized. In this case the wrapping acts as a resistance barrier to the self-contained biological indicator unit. The sterilant must pass through the wrapping, penetrate the self-contained unit in order to reach the spore strip and, with sufficient exposure time, kill the spores.
To help standardize the biological test procedure within hospitals, AAMI (Association for the Advancement of Medical Instrumentation) has established standards for the making of biological test packs for ETO gas sterilization. The standard calls for placement of the self-contained biological in a 10 MM syringe with the plunger pushed down to hold it in place. The syringe is then wrapped in a disposable towel and placed inside a paper/plastic peel pouch. This configuration is then considered a biological test pack for EO gas sterilization testing.
In order to provide more reliable, consistent and cost effective results, several companies have made totally disposable EO biological test packs which duplicate the performance of the "Standard" packs defined by AAMI. These test packs are typically made of porous paper and other material substitutes. An example of this type of pack is made by the ATI Division of PyMaH Corporation, recently purchased by 3M Corporation. This disposable EO biological test pack is made of the same materials as the pack defined by AAMI except it is made on an assembly line and tested for accuracy. Very little economy is gained in this configuration but reliability is improved over the hospital constructed pack for the same purpose.
Other disposable biological test packs are also offered for sale by other U.S. companies. The American Sterilizer Company manufactures a disposable biological test pack which consists of a cardboard and plastic tube in the shape of a mailing tube inside of which is placed a self-contained biological as previously described. Rather than surgical wrap and paper, air is used as the insulating material. The sterilant enters the tube through the seams or through a hole placed and subsequently the spores which reside inside it. Surgicot, Inc., manufactures a similar product to ATI's for the ETO gas biological test pack. 3M has yet a different biological test pack for ETO gas sterilization. It uses two sheets of plastic which form a web with a narrow opening which weaves in semicircles across the face of the surface to form a tortuous path for the ETO gas to follow before it encounters the self-contained unit which holds the spore strip.
Although, such disposable biological test packs have less bulk than the aforementioned towel and syringe packs, there is still a need for a smaller more economical biological test pack for ETO gas sterilization which performs the same function as the AAMI standard pack as previously described. By using fewer and less expensive components, a more cost effective test pack can be made. Rather than porous paper materials which are themselves bulky, the present invention uses mainly small, precision molded plastic parts. A porous plastic or porous paper plug is used as the resistance barrier to the sterilant. This test pack can be easily made and assembled and does not take the space of most commercially available biological test packs.